Mr. Smith was murdered in Kansas City. The police determined that the time of death was
between 11:10 pm and 11:30 pm. Four suspects were questioned: Butler, the butler; Cook,
the cook; Ruby, the maid; and Irma, Mr. Smith’s secretary.

The suspects made the
following statements:
Butler: I did not do it. Irma did it. Mr. Smith was blackmailing Irma. Ruby and I were
watching television together from 10:10 p.m. until 12:30 a.m.
Cook: I am innocent. Irma was being blackmailed. Butler murdered Mr. Smith. I saw
Irma leave the house at 10:00 p.m.
Ruby: I am innocent. Butler and I were watching television together at the time of the
murder. Irma was being blackmailed. I saw Irma speaking to Mr. Smith at 9:30
p.m. on the night of the murder.
Irma: I did not kill Mr. Smith. I was not being blackmailed. I was in St. Louis during
the entire night of the murder. Ruby is the murderess.

If each suspect made exactly two true statements and told exactly two lies, determine who
killed Mr. Smith.

Thank you very much for adding the not-so-clearly-implied constraint and providing a full solution based upon it.I was on a short "vacation" in Paris and during its duration had not a iota of "leisure time" to comment upon this significant omission.

Out of four net days in this elegant city three were fully devoted to some business I had to attend while Saturday was left to sightseeing, Pissaro's exhibition in Musee Marmottan Monet and dining with old friends.

On my way back I had some overlay time at the Istanbul's Attaturk Airport where I have found: 1. there was no free WI-FI and 2. using my smartphone to type a message like this was too time-consuming and 3. delaying it for another day or two will harm no one.